查看更多>>摘要：In recent years,tungsten disulfide(WS2)and tungsten selenide(WSe2)have emerged as favorable electrode materials because of their high theoretical capacity,large interlayer spacing,and high chemical activity;nevertheless,they have relatively low electronic conductivity and undergo large volume expansion during cycling,which greatly hinder them in practical applica-tions.These drawbacks are addressed by combining a superior type of carbon material,graphene,with WS2 and WSe2 to form a WS2/WSe2@graphene nanocomposites.These materials have received considerable attention in electro-chemical energy storage applications such as lithium-ion batteries(LIBs),sodium-ion batteries(SIBs),and supercapacitors.Considering the rapidly growing research enthusiasm on this topic over the past several years,here the recent progress of WS2/WSe2@graphene nanocomposites in electrochemical energy storage appli-cations is summarized.Furthermore,various methods for the synthesis of WS2/WSe2@graphene nanocomposites are reported and the relationships among these methods,nano/microstructures,and electrochemical performance are systematically summarized and discussed.In addition,the challenges and prospects for the future study and applica-tion of WS2/WSe2@graphene nanocomposites in electro-chemical energy storage applications are proposed.
查看更多>>摘要：Aqueous zinc-ion batteries(ZIBs)combine the benefits of metallic Zn anodes with those of aqueous electrolytes and are well suited for large-scale energy storage because of their inherent high safety,cost-effec-tiveness,and eco-friendliness.Currently,the practical application of such batteries is hindered by the poor cycling performance of Zn anodes due to uncontrolled dendrite formation and severe side reactions,although recent reports suggest that these problems can be mitigated through the modification of Zn anodes with metal-based materials.Given that the mechanisms of improving Zn deposition and the structural evolution of metal-based materials have not been systematically reviewed,we herein systematically overview the metal-based materials used to stabilize Zn anodes,starting with a brief summary of the anode working mechanism and the challenges faced by stabilized Zn anodes.Subsequently,the design principles of Zn anodes stabilized by metal-based materials and the related recent progress are reviewed,and the key challenges and per-spectives for the future development of such Zn anodes are proposed.
查看更多>>摘要：Lithium-ion batteries(LIBs)with extreme fast charging(XFC)capability are considered an effective way to alleviate range anxiety for electric vehicle(EV)buyers.Owing to the high ionic and electronic conductivity of LiNixCoyMnzO2(x+y+z=1,NCM)cathodes,the inevitable Li plating of graphite in NCM | graphite cell is usually identified as a key bottleneck for XFC LIBs.However,the capacity decay mechanism of cathode materials under XFC has not been fully investigated.In this work,three typical NCM cathode materials with different Ni fractions were chosen and their electrochemical per-formances under XFC associated with structural evolution were investigated.A faster capacity decay of NCMs under XFC conditions is observed,especially for Ni-rich NCMs.In-situ X-ray diffraction(XRD)reveals that the multiple c-axis parameters appear at the high-voltage regions in Ni-rich NCMs,which is probably triggered by the larger obstruction of Li(de)intercalation.Particularly,NCMs with moderate Ni fraction also present a similar trend under XFC conditions.This phenomenon is more detrimental to the structural and morphological stability,resulting in a faster capacity decay than that under low current charging.This work provides new insight into the degradation mechanism of NCMs under XFC conditions,which can promote the development of NCM cathode materials with XFC capability.
查看更多>>摘要：Considering the intrinsic advantages of natural copiousness and cost-effectiveness of potassium resource,potassium-ion batteries(KIBs)are booming as prospective alternatives to lithium-ion batteries(LIBs)in large-scale energy storage scenarios.Nevertheless,lacking desirable electrodes for reversibly hosting the bulky K+hinders the widespread application of KIBs,and it needs to be urgently solved.Hereon,the porous S-doped Sb2O3-graphene-car-bon(SAGC)nanofibers are manufactured through an adjustable and facile approach,which involves electro-spinning,in situ etching and sulfuration.The synthesized SAGC is featured by the ultra-small amorphous Sb2O3 homogeneously wrapped inside the carbon matrix,as well as the co-incorporation of graphene and sulfur.Tentatively,the SAGC nanofiber sheets are applied as binder-free anodes for KIBs,exhibiting a prominent cycling life(256.72 mAh·g-1 over 150 cycles at 100 mA·g-1)and rate ·g-1 over 100 cycles at 1 A g-1).The positive synergy among all the active components accounts for the distin-guished performances of the SAGC.By reinforcing the tolerability to the swelling stress,producing the valid electrochemical active sites,and promoting the charge transferring for reversible K+uptake,the SAGC finally renders the excellent cyclability,capacity,and rate capa-bility.Moreover,the extrinsic electrochemical pseudoca-pacitance characteristics induced by the porous carbon substrate elevate the K-storage capacity of the SAGC as well.It is hoped that the conclusions drawn may offer new insights into a direction for the high-performance binder-free KIB anodes.
查看更多>>摘要：Lithium-ion capacitors(LICs)of achieving high power and energy density have garnered significant atten-tion.However,the kinetics unbalance between anode and cathode can impede the application of LICs.Vanadium nitride(VN)with a high theoretical specific capacity(～1200 mAh·g-1)is a better pseudocapacitive anode to match the response of cathode in LICs.However,the insertion/extraction of Li-ions in VN's operation results in significant volume expansion.Herein,the VN/N-rGO-5 composite that three-dimentional(3D)dicyandiamide-derived-carbon(DDC)tightly wrapped VN quantum dots(VN QDTs)on two-dimentional(2D)reduced graphene oxid(rGO)was prepared by a facile strategy.The VN QDTs can reduce ion diffusion length and improve charge transfer kinetics.The 2D rGO as a template provides support for nanoparticle dispersion and improves electrical conductivity.The 3D DDC tightly encapsulated with VN QDTs mitigates agglomeration of VN particles as well as volume expansion.Correspondingly,the LICs with VN/N-rGO-5 composite as anode and activated carbon(AC)as cathode were fabricated,which exhibits a high energy density and power density.Such strategy provides a per-spective for improving the electrochemical properties of LIC anode materials by suppressing volume expansion and enhancing conductivity.
查看更多>>摘要：Tin-based materials with high theoretical capacity and suitable working voltage are ideal anode materials for lithium-ion batteries(LIBs).However,to overcome their shortcomings(volume expansion and inferior stability),the preparation processes are usually complicated and expensive.Herein,a tin-based metal-or-ganic complex(tin 1,2-benzenedicarboxylic acid,Sn-BDC)with one-dimensional microbelt morphology is synthesized by a facile,rapid and low-cost co-precipitation method,and served as anode material for LIBs without any post-treat-ment.Sn-BDC exhibits a high reversible capacity with 609/440 mAh·g-1 at 50/2000 mA·g-1,and robust cycling stability of 856 mAh·g-1 after 200 cycles at 200 mA·g-1,which are obviously superior to that of the SnOx/C coun-terparts.Moreover,an electrochemical reconstruction per-spective on the lithium storage mechanism of Sn-BDC is proposed by systematic ex-situ characterizations.The reconstructed SnO2 replaces Sn-BDC and becomes the active material in the subsequent cycles.As the by-product of the lithiation reaction,the formed Li-based metal-or-ganic complex(Li-BDC,wrapped around the reconstructed SnO2)plays an important role in alleviating volume expansion and accelerating the charge transfer kinetics.This work is beneficial to design and construct the new electrode materials based on the electrochemical recon-struction for advanced LIBs.
查看更多>>摘要：Water washing has been regarded as one of the most effective strategies to remove surface residual lithium of nickel-rich layered oxides for lithium-ion batteries(LIBs).However,the loss of lattice lithium during the water washing process deteriorates the electrochemical performances and air stability.Herein,washing the LiNi0.90Co0.08Al0.02O2(NCA)with ammonium dihydrogen phosphate(NH4H2PO4)solution has been proposed to simultaneously enhance electrochemical performances and air stability,in which in-situ generated Li3PO4 coating layer on surface of NCA can suppress the loss of lattice lithium.Besides,as a fast ionic conductor,Li3PO4 coating layer on NCA can prevent the direct contact with elec-trolyte/air.As a result,the NH4H2PO4 solution washed NCA cathode can deliver a high capacity of 131.9 mAh·g-1 at 10.0C rate as well as impressive cycle stability with a capacity retention of 83.1％after 100 cycles at 1.0C,much higher than those of water washed NCA(WS-NCA)electrode.After exposed in air for 7 days,the NH4H2PO4 solution washed NCA electrode can more effectively maintain the structural integrity as well as the electrochemical performances than water-washed NCA.This work provides a simple and effective approach to enhance the cycle stability and air stability of Nickel-rich cathode materials.
查看更多>>摘要：Vanadium disulfide(VS2)as a typical two-di-mensional transition metal chalcogenide has excellent competitiveness for sodium-ion storage due to its wide layer spacing(0.575 nm),high theoretical capacity of 932 mAh·g-1 originating from multi-electron electrochemical redox.However,continuous sodiation process accompa-nied by crystal structural evolution and collapse cause rapid capacity decaying.Herein,novel few-layer VS2 nanosheets with open(001)crystal planes are in-situ constructed on reduced graphene oxide to solve these issues mentioned above.It indicates that few-layer VS2 provides more Na+storage activity due to the low Na+surface migration energy barrier on exposed crystal(001)planes.The flexible and high electronic conductivity of carbon matrix also effectively builds multi-level buffer structure and electron transport kinetics to boost the Na+insertion/conversion reactive activity on VS2 as well as Na+pseudocapacitance storage kinetics on edges and defects of nanosheets.Those coupling effects result in high rate capability and long cycling stability as a battery/ca-pacitor anode.It delivers conspicuous high energy density of 81 and 40 Wh·kg-1 at power density of 118 and 10,286 W·kg-1,as well as 80％energy retention rate after 5000 cycles,confirming its great application potential in sodium-based storage devices.
查看更多>>摘要：The effect of partial substitution of Mg for Ni on a high-sodium and lithium-free layered P2-type Na45/54Mg6/54Ni12/54Mn34/54O2 cathode with high initial Coulombic efficiency and excellent cyclic stability has been investigated in this study.Based on the crystal structural analysis,the Mg doping can retain the P2 structure up to 4.3 V,thus restraining the detrimental phase transformation of P2-O2 during the Na-ion intercalation/deintercalation process.Therefore,the obtained Mg-doped P2-type cathode exhibits a reversible specific capacity of 109 mAh·g-1 at 0.1C between 2.0 and 4.3 V and a retention rate of 81.5％after 200 cycles at 1C.In addition,the full cell consisting of Mg-doped P2-type cathode and hard carbon anode shows a capacity retention rate of 85.6％after 100 cycles.This study provides new insight into the development of durable cathode mate-rials for sodium-ion batteries.
查看更多>>摘要：Hard carbon derived from bamboo for the anode material of sodium-ion batteries has a three-dimensional(3D)open framework structure and has naturally incorpo-rated K-ions into its carbon structure,increasing the d-interlayer spacing of hard carbon materials for facilitating Na+transport.In this work,bamboo-derived hard carbon was prepared via two carbonization temperatures at 700 and 1000 ℃ for an hour and employed as an anode for sodium-ion batteries(SIB).X-ray diffraction(XRD)and Fourier transform(FT)-Raman spectroscopic results indi-cated the disordered structure with d-spacing(d002)around 0.36-0.37 nm,which is a benefit for sodium ion insertion/desertion.Herein,the composition between carbon-nan-otube(CNT)and bamboo-derived hard carbon(BB)was synthesized by a ball mill with various contents of CNT(1 wt％,5 wt％and 10 wt％).At the optimal CNT content of 5 wt％,the sample exhibited excellent performance and outstanding stability.As the anode,the half-cell SIB using BB(700)w@5％CNT(with a carbonization temperature of 700 ℃ and CNT loading of 5 wt％)delivered a high initial specific capacity of 268.9 mAh·g-1 at 0.1C and capacity retention of 78.6％after 500 cycles at 1.0C.The full cell SIB fabrication BB(700)w@5％CNT in combination with Na3V2(PO4)3 as the cathode demonstrated a high specific capacity of 127.6 mAh·g-1 at 0.2C with its capacitive retention remaining of 78％at 1.0C after 1000 cycles.The attained storage performance indicates that hard carbon-CNT composite anode material enhanced the conductive path of electron transport and provided long-term cycling stability.The good electrochemical performance as well as the low cost and environment-friendliness of the bamboo-derived hard carbon proves its suitability for future sodium-ion batteries.
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